Thermal and acoustical insulating shields, to which the present invention is an improvement, have long been known in the art. Such shields are used in a wide variety of applications, among which are shielding in space crafts, automobiles, home appliances, electronic components, industrial engines, boiler plants and the like. Some of such shields have proportionally smaller thermal insulating value and proportionally higher acoustical insulating value, and vice versa. There are, of course, shields which lie therebetween.
In connection with the thermal insulating value, shields are known which provide thermal insulation, primarily, by virtue of being a radiation thermal shield, while others provide thermal insulation by being, primarily, a conduction thermal shield, and, again, there are shields that lie therebetween. For example, pressed and formed sheet metal has long since been mounted by bolts, nuts, screws, welding, etc. between an object to be protected, i.e. shielded, for example, the floor pan of an automobile, and a heat source, for example, a portion of the exhaust system of the automobile. Such a formed sheet metal provides thermal insulation, primarily, by re-radiation of heat from the portion of the exhaust system back into the ambient and/or other cooler parts of the undercarriage of an automobile to thermally insulate the floor pan from that portion of the exhaust. Such sheet metal shields, however, have low acoustical insulating value, and a large portion of noise produced in an adjacent portion of an exhaust system can be transmitted through the floor pan of the automobile and into the passenger compartment. Additional noise can be produced by loose shields which vibrate and/or rattle. Such sheet metal shields, also, provides thermal insulation value in connection with conductive heat, since such sheet metal shields will be spaced between the floor pan and the portion of the exhaust, and that spacing provides an air gap between the shield and the floor pan which reduces conductive, and to some extent, convective heat transfer.
Where substantial acoustical shielding is also required, metal shields, as described above, are not satisfactory. In such requirements, the shields generally are at least in part fibrous in nature, e.g. batts of fiberglass, which provide increased acoustical insulation as well as good conduction thermal insulation. However, such insulation can only be used where there are insignificant forces, both static and dynamic, on the fibrous insulation, since batts of fiberglass, for example, have very little strength in any direction, i.e. in either the X, Y or Z directions. Such shields are, however, very useful in certain applications, for example, thermal insulation in domestic dishwashers.
A very particular problem in regard to such shields has been encountered by the automobile industry and like industries, and that problem has become acute in recent years. As the overall size of automobiles continues to shrink, space within any portion of the assembled automobile is now at a premium. For example, in past designs of automobiles, sufficient room existed between the exhaust system of the automobile and the floor tunnel of the automobile that the usual sheet metal shield could be suspended in the tunnel, e.g. with bolts, screws, welding and the like, with specially provided ears or dogs or connectors, so as to space that sheet metal shield from the tunnel and from the exhaust system. This provided a radiation barrier to heat transfer from the exhaust system to the tunnel, as well as a conductive and convective heat transfer barrier in view of the spacing between the shield and the tunnel. This design also provided some acoustical insulation. However, with modern designs, the spacing between the exhaust system and the tunnel is now very much reduced, and in many situations, it is now no longer practical to suspend shields between the exhaust and tunnel, and, moreover, the reduced spacing correspondingly reduces any air gap remaining between the shield and the tunnel, such that very little conductive and convective heat insulation or acoustical insulation results.
The art has long recognized that fibrous batts, usually containing inorganic fibers, such as glass fibers, mineral and clay wool fibers, alumina-silicate fibers, silica fibers and the like provide very good thermal and acoustical insulation and could potentially be a replacement for the suspended sheet metal shields. The problem with such insulation is that the batts, especially of such inorganic fibers, are usually made by air laying fibers onto a moving belt, and, hence, the fibers tend to stratify in non-discrete layers throughout the thickness (Z direction) of the batts. Since these fibers are not substantially interlocked in the z direction, the batt has very low Z-directional tensile strength. Even under static loading of its own weight, for example, a batt of fiberglass will simply sag out of its original configuration when suspended from an upper surface thereof. The art has, therefore, expended substantial effort in attempting to provide greater tensile strength to such fibrous batts, in regard to both the X and Y directions and the Z direction.
An early attempt in this regard is disclosed in U.S. Pat. No. 3,975,565 to Kendall, which proposes a composite structure of layered inorganic fibers and organic fibers which are needled together to provide insulating batts (both thermal and acoustical) which have greater tensile strengths in all directions, especially in the Z direction. In this approach, an inorganic fiber layer, such as that of glass fibers, is sandwiched between two layers of organic fibers, for example, cellulose acetate fibers, and needling of the composite sandwiched layers is achieved from either one or both sides of the composite so as to drive portions of the organic fibers from the organic fiber layer(s) through the inorganic fiber layer (glass fibers) and, thus, to tack the composite together and, particularly, improve the Z-directional strength. However, because of the needling technique used in that process, the needle punch density could not be greater than about 260 needle punches per square inch, since, at above about 260 needle punches per square inch, glass fiber damage resulted and with a more than 25% loss of mat strength. While such an approach certainly improved Z-directional strength, with such low numbers of needle punches, the Z-directional strength of such a composite is still quite low and unacceptable for most modern thermal/acoustical insulating applications where substantial static and dynamic forces are placed on that insulation, e.g. in suspended use with an automobile, as discussed above.
In U.S. Pat. No. 4,237,180 to Jaskowski, it is proposed to improve such composite thermal and acoustical insulating batts by including in the inorganic fiber layers heat shrinkable organic fibers. After needling, the composite batt is subjected to temperatures sufficient to cause the organic fibers to shrink, e.g. at least 40% in length, whereby the shrinking fibers mechanically interlock the inorganic fibers into a more consolidated form and therefor improve the strength, particularly in the Z direction. However, shrinking fibers is not only a difficult process, but is substantially uncontrollable, and this approach does not result in uniform products. Moreover, the tensile strengths, and particularly the Z-directional tensile strengths, are not greatly improved by that process.
U.S. Pat. No. 4,522,876 to Hiers recognizes the problems noted above and specifically addresses the problem of a low number of needle punches described in the Kendall patent and the undesired results thereof. The Hiers patent takes a different approach in that it achieves high numbers of needle punches per square inch by the technique of ensuring that the barbs of needles passing through an organic fiber outer layer(s) are loaded with the organic fibers of that layer(s) before the barbs reach the adjacent glass fiber layer. Since the barbs are filled with organic fibers, the barbs cannot engage and break the glass fibers as the needles pass through the glass fiber layer, and the resulting batt can be highly needled with exceptional Z-directional strength, as well as greatly improved X- and Y-directional strengths. While this approach is a very decided advance in the art, it still encounters difficulties when such batts experience high static and dynamic loadings, such as in the case of an automobile with a suspended shield, as described above. These difficulties will be more clear hereinafter.
A somewhat different approach in the art is described in U.S. Pat. No. 4,851,274 to D'Elia. In that approach, onto a needlable substrate is placed a middle layer of mineral fibers of short lengths such as to preclude interlocking of other fibers of the structure. A top layer of organic fibers is placed thereon. Needling is then achieved through that top layer and middle layer to the substrate with needle punches up to about 3,000 per square inch. Since the inorganic fibers are not substantially interlocked, the web becomes quite flexible and a binder can be applied to that structure, such as a phenolic binder, and set for forming a moldable thermal and acoustical shield useful, for example, as trunk liners. However, the use of a synthetic resin to achieve formability of such a shield is a decided disadvantage, since it is quite expensive to use a binder, and, moreover, the shield must be molded with conventional tools and dies, which themselves are quite expensive.
U.S. Pat. No. 4,996,095 to Behdorf et al attempts to solve the problem by yet a further approach. In that patent, it is proposed that a glass fiber mat be bonded to a sheet of aluminum by an adhesive of a particular nature and that the adhesive-joined composite can be used as a shield between an automobile floorboard and an exhaust system. The composite of the aluminum sheet and glass fiber mat is shaped to the contours of the vehicle by conventional processes, such as deep drawing, combined deep drawing-stretching forming, bending and crimping. The so-formed shield is then applied to the vehicle by a special clamp. While this approach provides a good thermal and acoustical insulation, it still requires conventional forming techniques, as noted above, to configure the shield to the object to be protected and also requires special clamps for affixing the shield to the vehicle. All of this is expensive and time consuming in assembly of the automobile and does not solve the problem or severely limited space in modern designs, as noted above.
As can be appreciated from the above, it would be of particular advantage in the art to provide a thermal and acoustical insulating shield which is flexible, so that it may be manually applied to the vehicle contours, or other structure, without having to be preformed in conventional shaping processes, and which shield is adhesively attachable to the object to be protected and without the need of any mechanical attaching devices, such as clamps, bolts, screws, welds and the like.
In the above-noted U.S. patent application Ser. No. 09/033,852, a flexible, adhesively attachable thermal and acoustical insulating shield is disclosed. According to the invention disclosed in that application, it was found that the needling technique of U.S. Pat. No. 4,522,876, described above, could be modified such that, in needling organic fibers from the organic fiber layers sandwiching the inorganic fiber layer, tufts of the organic fibers can protrude from opposite outer sides of the organic fiber layers so as to form a tufted upper surface and a tufted lower surface of the needled batt.
An adhesive is applied to the tufted upper surface and tufted lower surface of the batt, such that the tufts on the upper and lower surfaces are secured to those surfaces by the adhesive. This prevents the tufts from being pulled from that surface during high static or dynamic loading of the shield, as would be encountered by use in an automobile, and, thus, provide very high Z-directional strength to that composite batt.
To the adhesive applied on the lower surface of the batt, a flexible protective foil is permanently adhered by the adhesive to the lower surface of the batt. This provides a lower protective surface to the composite batt to prevent mechanical damage, e.g. from rocks and other debris on the road, while at the same time providing radiation insulation to the shield.
The adhesive on the upper surface of the batt is an activatable adhesive, such as a pressure-sensitive adhesive and a flexible, strippable foil is releasably adhered to a pressure-sensitive adhesive on the upper side of the batt, such that, by removing the strippable foil, the shield may be merely flexed and pressed to configure and permanently attach the upper surface of the shield to the object to be shielded. Thus, no forming apparatus or attachment means, such as clamps, bolts, screws, welds and the like, are required to permanently configure and place the shield onto the vehicle, e.g. underneath the floor pan to protect the floor pan from exhaust components.
When the batt of the composite organic and inorganic fibers is of certain thicknesses and the protective foil is of certain materials and certain thicknesses, the shield can be easily manually deformed by a worker when placing the shield next to the contours of the object to be protected, and, accordingly, no preforming, such as conventional stamping, drawing, etc., is required, although such preforming can be practiced if desired.
Since the shield is adhesively attached directly to the object to be protected, there is no need for a clearance between the object to be protected, e.g. the floor pan, and the shield itself, which allows the use of that shield in the very restricted and diminished spaces of modern automobile designs. However, with the combination of the protective foil, particularly when that foil is a radiation barrier foil, and the composite batt, high thermal insulation and high acoustical insulation results.
When pressing the protective foil and/or the strippable foil to the adhesive covered upper and lower tufted surfaces and when pressing the shield to the contours of the object, the tufts on the surfaces, embraced by the adhesive, tend to bend and compress from the vertical, further locking those tufts into the surfaces of the batt. This provides even greater strength to the batt in the Z direction, because the bent or compressed tufts, somewhat like bradding, become very difficult to separate from the surfaces of the batt and, thus, hold that batt in the Z direction with great strengths, and which strengths can avoid separations of the batt during high static and dynamic loadings on the batt.
Thus, the invention in that application provides a flexible, adhesively attachable, thermal and acoustical insulating shield. The shield has a needled, flexible, fibrous batt having an insulating layer of insulating fibers disposed between opposite binding layers of binding fibers. Binding fibers of each binder layer are needledly disposed through the insulating layer and an opposite binding layer to provide tufts of binding fibers protruding from that opposite binding layer. This forms a tufted upper surface and a tufted lower surface of the batt. An adhesive is disposed and adhered substantially over the upper tufted surface and the lower tufted surface of the batt such that the tufts on the tufted upper and tufted lower surfaces are secured to those surfaces by the adhesive. A flexible, protective foil is permanently adhered by the adhesive to the tufted lower surface of the batt.
The shield may be flexed and pressed to configure and permanently attach the upper surface to an object to be protected.
The invention in that application also provides a method of applying the shield of the invention to an object to be thermally and acoustically protected. In this method, the upper surface of the batt, with the adhesive exposed thereon, is pressed at the protective foil sufficiently to configure the shield to the contours of the object to be protected, and the pressure-sensitive adhesive is caused to permanently adhere to the contours of that object. Thus, by this method, the shield can be placed directly and permanently on the object to be protected and without the need of any attachment devices, such as bolts, screws, welds, clamps and the like.
The invention of that application also provides that the shield may be closed at its peripheries, as shown in FIG. 8 of that application, where the insulating batt is enclosed within protective foils by sealing the peripheries of those protective foils and then placing the pressure-sensitive adhesive and strippable foil on the top thereof. This arrangement prevents egress of moisture, contamination, dirt, dust and the like into the insulating material, which is a very desirable feature, but that approach does require two protective foils, sandwiching the insulating material, with the peripheries of the foils being sealed in a separate sealing step. It further requires the separate step of placing the adhesive and the strippable foil on the upper surface of the uppermost protective foil.
As can be appreciated, this results in a more expensive insulating shield, and in that sense, the arrangement for enclosing the insulating material is not as desired.
It would, therefore, be of substantial advantage to the art to provide means of sealing the insulating material of that application from egress of moisture, dust, dirt and other road contamination without the additional expense of the arrangement noted in that application, as briefly discussed above. It would, further, be of a substantial advantage to the art to make such shield a self-sealing shield, so as to prevent egress of moisture, dust, dirt and the like.